Content node selection based on classless prefix

ABSTRACT

Systems, methods, apparatuses, and software that announce prefixes associated content nodes of a content delivery network are provided herein. In one example, a method of operating a communication system comprising Internet service providers configured to exchange content requests between end user devices and content nodes is presented. The method includes assigning a content node of the content delivery network a first Internet Protocol (IP) address having an associated first short prefix and a first long prefix, and assigning the content node a second IP address having an associated second short prefix and a second long prefix. The method also includes announcing the first short prefix and the first long prefix to a first Internet service provider communicatively coupled to the content node, and announcing the second short prefix and the second long prefix to a second Internet service provider communicatively coupled to the content node.

RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.Non-Provisional patent application Ser. No. 14/485,381, entitled“CONTENT NODE SELECTION BASED ON CLASSLESS PREFIX”, filed on Sep. 12,2014, which claims the benefit of U.S. Provisional Application Ser. No.61/920,957, entitled “CACHE NODE INTERNET PROTOCOL ADDRESS SELECTIONBASED ON CLASSLESS PREFIX,” and filed on Dec. 26, 2013, and which willgrant as U.S. Pat. No. 9,912,631 on Mar. 6, 2018, all of which arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

Aspects of the disclosure are related to the field of communicationnetworks, and in particular, to content delivery over communicationnetworks.

TECHNICAL BACKGROUND

Network-provided content, such as Internet web pages or media contentsuch as video, pictures, music, and the like, are typically served toend users via networked computer systems. End user requests for thenetwork content are processed and the content is responsively providedover various network links. These networked computer systems can includeorigin hosting servers which originally host network content of contentcreators or originators, such as web servers for hosting a news website.However, these computer systems of individual content creators canbecome overloaded and slow due to frequent requests of content by endusers.

Content delivery networks have been developed which add a layer ofcaching between the origin servers of the content providers and the endusers. The content delivery networks typically have one or more cachenodes distributed across a large geographic region to provide faster andlower latency access to the content for the end users. When end usersrequest content, such as a web page, which is handled through a cachenode, the cache node is configured to respond to the end user requestsinstead of the origin servers. In this manner, a cache node can act as aproxy for the origin servers. However, when a cache node communicatesover different communication service providers, such as Internet ServiceProviders (ISPs), the various ISPs and other datagram networks overwhich end user content requests and content delivery are handled can addadditional slowdowns and latency issues.

The Internet Protocol (IP) is a standard for routing communicationthrough and between packet-switched networks. The unit of delivery in IPis the datagram, a packet of digital data that includes a routingheader. The header includes the IP address of the intended destinationof the datagram. An IP address is a unique number. In IP version 4, anIP address has 32 bits. In IP version 6, an IP address has 128 bits. Asa datagram is routed, it is transferred between various routers untileventually reaching its destination. Each router uses a routing table todecide to which other router the datagram should be forwarded next.Routers frequently share information to update their routing tablesusing standard interactions such as Border Gateway Protocol.

An IP address is split logically into two parts: high-order bits andlow-order bits. The last router of a route uses the low-order bits toidentify which device is the final destination of a datagram. The otherrouters of a route ignore the low-order bits and use the high-order bitsto transfer the datagram from one interconnected network to another.Exactly how many bits are high-order or low-order depends on the routingscheme. Classful routing allows only 8, 16, or 24 bits to be high-order,which can present problems. Classful routing can lead to many entries inrouting tables which reduces efficiency in some network topologies.Classful routing does not take advantage of the increased address sizeof IP version 6, and the availability of unique numbers within thelimited space of at most 24 high-order bits does not meet demand forcustom topologies. Classless Inter-Domain Routing (CIDR) alleviatesthese problems by allowing an arbitrary number of high-order bits. CIDRnotation is an extended encoding of an IP address that includes a prefixsize. The prefix size declares how many bits are high-order, which isthe CIDR prefix.

OVERVIEW

Systems, methods, apparatuses, and software that announce prefixesassociated content nodes of a content delivery network are providedherein. In one example, a method of operating a communication systemcomprising Internet service providers configured to exchange contentrequests between end user devices and content nodes is presented. Themethod includes assigning a content node of the content delivery networka first Internet Protocol (IP) address having an associated first shortprefix and a first long prefix, and assigning the content node a secondIP address having an associated second short prefix and a second longprefix. The method also includes announcing the first short prefix andthe first long prefix to a first Internet service providercommunicatively coupled to the content node, and announcing the secondshort prefix and the second long prefix to a second Internet serviceprovider communicatively coupled to the content node.

In another example, a computer apparatus to operate a management systemfor a content delivery network that handles content requests for enduser devices using content nodes is presented. The computer apparatusincludes processing instructions that direct the management system, whenexecuted by the management system, to assign a content node of thecontent delivery network a first Internet Protocol (IP) address havingan associated first short prefix and a first long prefix, assign thecontent node a second IP address having an associated second shortprefix and a second long prefix, announce the first short prefix and thefirst long prefix to a first Internet service provider communicativelycoupled to the content node, and announce the second short prefix andthe second long prefix to a second Internet service providercommunicatively coupled to the content node. The computer apparatus alsoincludes one or more non-transitory computer readable media that storethe processing instructions.

In another example, a management system for a content delivery networkthat handles content requests for end user devices using content nodesis presented. The management system includes a processing systemconfigured to assign a content node of the content delivery network afirst Internet Protocol (IP) address having an associated first shortprefix and a first long prefix, and assign the content node a second IPaddress having an associated second short prefix and a second longprefix. The management system also includes a communication interfaceconfigured to announce the first short prefix and the first long prefixto a first Internet service provider communicatively coupled to thecontent node, and announce the second short prefix and the second longprefix to a second Internet service provider communicatively coupled tothe content node.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present disclosure.

Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the views. While multiple embodiments aredescribed in connection with these drawings, the disclosure is notlimited to the embodiments disclosed herein. On the contrary, the intentis to cover all alternatives, modifications, and equivalents.

FIG. 1A is a system diagram illustrating a communication system.

FIG. 1B is a system diagram illustrating a communication system.

FIG. 1C is a system diagram illustrating a communication system.

FIG. 2A is a flow diagram illustrating an example method of operating acommunication system.

FIG. 2B is a flow diagram illustrating an example method of operating acommunication system.

FIG. 3 is a system diagram illustrating a communication system.

FIG. 4 is an index of route prefixes.

FIG. 5 is a sequence diagram illustrating an example method of operatinga communication system.

FIG. 6 is a sequence diagram illustrating an example method of operatinga communication system.

FIG. 7 is a block diagram illustrating a management system.

DETAILED DESCRIPTION

Network content, such as web page content, typically includes contentsuch as text, hypertext markup language (HTML) pages, pictures, video,audio, code, scripts, or other content viewable by an end user in abrowser or other application. This various network content can be cachedby the content nodes of a content delivery network. The network contentcan include website content, pictures, video, other media, dynamiccontent, and other content, including combinations thereof. When acontent delivery network is employed, content nodes of the contentdelivery network can act as a proxy to cache content for deliverybetween origin servers and end user devices.

The content delivery networks typically have one or more content nodesdistributed across a large geographic region to provide faster and lowerlatency local access to the content for the end users. When end usersrequest content, such as a web page, a locally proximate content nodewill respond to the content request instead of the associated originserver. Various techniques can be employed to ensure the content noderesponds to content requests instead of the origin servers, such asassociating web content of the origin servers with network addresses ofthe content nodes instead of network addresses of the origin serversusing domain name system (DNS) registration and lookup procedures.

As a first example employing a content delivery network, FIGS. 1A-1C arepresented. FIGS. 1A-1C are system diagrams illustrating communicationsystem 100. Communication system 100 includes end user device 101,content delivery network 110, Internet Service Providers (ISP) 141-142,Internet 150, and origin server 190. Content delivery network 110includes one or more content nodes, such as content nodes 120-121.Content delivery network 110 and ISP 141 communicate over link 180.Content delivery network 110 and ISP 142 communicate over link 181. ISP141 and Internet 150 communicate over link 182. ISP 142 and Internet 150communicate over link 183. End user device 101 and Internet 150communicate over link 184. Origin server 185 and content deliverynetwork 110 communicate over link 185. Although not shown in FIGS. 1A-1Cfor clarity, each link 180-185 can include further networks, links, andother elements.

Each of content nodes 120-121 have multiple associated IP addresses,such as those shown in table 170 in FIG. 1. In this example content node120 has IP addresses 131-132, and content node 121 has IP addresses133-134. Each of IP addresses 131-134 is associated with a long prefixhaving many high order bits. In this example each IP address isassociated with a different long prefix. IP address 131 has long prefixC, IP address 132 has a long prefix D, IP address 133 has a long prefixE, and IP address 134 has a long prefix F. A prefix may be a CIDRprefix, where short prefixes are “/24” CIDR prefixes and long prefixesare “/27” CIDR prefixes, although variations are possible. IP addresses131-134 are also associated with only two short prefixes having lesshigh order bits than the long prefixes. Specifically, IP addresses 131and 133 are associated with short prefix A, while IP addresses 132 and134 are associated with short prefix B.

Content delivery network 110 can include network routers or computersystems that announce prefixes to ISPs 141-142 for use in routingcontent requests to content nodes, such as content nodes 120-121. Anannouncement may comprise an IP route advertisement communicated to anISP along the control plane of a routing protocol such as the BorderGateway Protocol. An announcement may instead comprise customizedmessaging or notifications from content delivery network 110 to theassociated ISPs. Content delivery network 110 announces long prefixes Cand E to ISP 141 for use in routing content requests into contentdelivery network 110. Announcement message 161 can be employed toannounce long prefixes C and E to ISP 141. Content delivery network 110announces long prefixes D and F to ISP 142 for use in routing contentrequests into content delivery network 110. Announcement message 162 canbe employed to announce long prefixes D and F to ISP 142.

For each long prefix announced, content delivery network 110 alsoannounces a corresponding short prefix, if the short prefix has not yetbeen announced. The short prefix includes a subset of the highest orderbits of the corresponding long prefix. Content delivery network 110announces short prefix A to ISP 141 and short prefix B to ISP 142, asfurther illustrated in table 170. Announcement message 171 can beemployed to announce short prefix A to ISP 141. Announcement message 172can be employed to announce short prefix B to ISP 142.

Responsive to the announcements, ISPs 141-142 only propagate to Internet150 announcement messages 171-172 that include a short prefix, and donot propagate to Internet 150 announcement messages 161-162 that includea long prefix. Such selective propagation to Internet 150 ofannouncements affects how routing is performed for content requeststraveling through Internet 150 as destined for content nodes 120-121.Internet 150 uses the short prefixes to select either one of Internetservice providers 141-142 when routing content requests to content nodes120-121. A content request transferred by an end user that is associatedwith short prefix A is routed through ISP 141. Likewise, a contentrequest transferred by an end user that is associated with short prefixB is routed through ISP 142.

After the prefixes are announced, routing of content requeststransferred by end users may occur as illustrated in FIGS. 1B and 1C.End user device 101 is representative of an end user computing devicethat can issue content requests, such as a computing device or asmartphone operating a content browsing application. An ISP is selectedby content delivery network 110 based on a short prefix associated withan IP address indicated by the content request. A lookup service, suchas a DNS server, informs end user device 101 of an IP address at whichcached content is available. End user device 101 issues content requestsinto Internet 150 using the IP address, and the content requests aretransferred for delivery to an associated one of content nodes 120-121.

To further illustrate operations of communication system 100, FIGS.2A-2C are presented. FIGS. 2A-2C are each flow diagrams illustrating amethod of operation of FIGS. 1A-1C. Specifically, FIG. 2A illustratesoperations for announcing prefixes by communication system 100 of FIG.1A. FIG. 2B illustrates operations for handling content requests tocontent node 120, as detailed in FIG. 1B. FIG. 2C illustrates operationsfor handling content requests to content node 121, as detailed in FIG.1C.

Referring now to FIG. 2A, content node 120 is assigned (201) IP address131 that has short prefix A and long prefix C, and content node 121 isassigned (201) IP address 133 that has short prefix A and long prefix E.Content node 120 is also assigned (202) IP address 132 that has shortprefix B and long prefix D, and content node 121 is assigned (202) IPaddress 134 that has short prefix B and long prefix F. This assignmentcan be seen in FIG. 1A and table 170, where each content node 120-121 isassigned to IP addresses with associated short and long prefixes.Additional IP addresses and associated prefixes can be assigned to eachof content node 120-121.

In some examples, a management system is employed in content deliverynetwork 110 to assign IP addresses to associated content nodes andidentify associated prefixes. However, the content nodes themselves canbe pre-configured with associated IP addresses and prefixes or thecontent nodes can be identify and assign the IP addresses and prefixesamong themselves. Each IP address can be associated with a networkinterface card (NIC) of a content node, or a NIC can have several IPaddresses associated therewith. Also, each content delivery node 120-121is communicatively coupled to more than one ISP, such as ISPs 141-142over an associated IP address.

Content delivery network 110 announces (203) prefixes A and C to ISP141, and announces (203) prefixes A and E to ISP 141. Content deliverynetwork 110 also announces (204) prefixes B and D to ISP 142, andannounces (204) prefixes B and F to ISP 142. The announcement messagescan be one or more packet messages or other notifications that includeindications of the associated prefixes, along with any associatedrouting information for the prefixes and for the content nodes ofcontent delivery network 110. For example, announcement message 161 caninclude information to route traffic associated with a particular longprefix to a particular content node, while announcement message 171 caninclude information to route traffic associated with a particular shortprefix over a particular ISP.

In FIG. 1A, announcement message 161 is employed over link 180 toannounce prefixes C and E to ISP 141, and announcement message 171 isemployed over link 180 to announce prefix A to ISP 141. Similarly,announcement message 162 is employed over link 181 to announce prefixesD and F to ISP 142, and announcement message 172 is employed over link181 to announce prefix B to ISP 142. In some examples, separate messagesor notifications are employed to announce prefixes C and E, and separatemessages or notifications are employed to announce prefixes D and F.Also, in some examples, combined announcement messages or notificationsare used, where a first announcement message is employed for allannouncements to ISP 141 and a second announcement message is employedfor all announcements to ISP 142. Other announcement message ornotification configurations are possible.

Each content node 120-121 of content delivery network 110 can transferannouncement messages or a management node of content delivery network110 can transfer the announcement messages. Likewise, each content node120-121 can communicate with the associated ISPs using one or morecommunication links, even though only one representative link isillustrated in FIG. 1A. Router or management nodes in each ISP canreceive the announcement messages transferred by elements of contentdelivery network 110. These router or management nodes in each ISP canresponsively modify routing tables or routing control processescommensurate with the announcement messages.

Once ISPs 141-142 receive the announcement messages, ISPs 141-142 canfurther transfer announcement messages 171-172 for delivery to Internet150. Router or management nodes in Internet 150 can receive theannouncement messages transferred by each ISPs 141-142. ISPs 141-142typically do not transfer long prefix announcements to Internet 150, andinstead only transfer short prefix announcement messages, such asannouncement messages 171-172. Thus, long prefixes C, E as well as shortprefix A are announced to ISP 141, while only short prefix A isannounced to Internet 150. Likewise, long prefixes D, F as well as shortprefix B are announced to ISP 142, while only short prefix B isannounced to Internet 150. Once the router or management nodes inInternet 150 receive the announcement messages, these elements ofInternet 150 can responsively modify routing tables or routing controlprocesses commensurate with the announcement messages.

Referring now to FIG. 2B, FIG. 2B illustrates operations for handlingcontent requests to content node 120-121, as detailed in FIG. 1B. InFIG. 1B, end user device 101 can reach content nodes 120-121 by way ofmore than one ISP, namely ISPs 141-142. To allow for switching betweenany of ISPs 141-142, the announcement of prefixes is completed asdiscussed in FIG. 2A. ISPs 141-142 might be selected among based oncurrent network conditions, link characteristics between end user device101 and content nodes 120-121, or other factors.

During operation, end user device 101 can browse content, such as via aweb browser or Internet content application, which a user canselectively request to view web pages, pictures, videos, dynamiccontent, or other network content associated with a web page. Typically,the web page will reference the associated network content using one ormore Uniform Resource Locators (URL) comprising a domain name and anyassociated path and server details. However, before any network contentcan be retrieved for display or use by end user device 101, a domainname is typically translated into a numerical network address. This canbe achieved using a Domain Name Service (DNS) lookup with a DNS lookupnode or DNS server.

In a first example, DNS lookup 177 in FIG. 1B is performed by end userdevice 101 which returns an IP address associated with the desirednetwork content cached by content node 120. The IP address can be eitherIP address 131 or IP address 132 for FIG. 1B to reach content node 120.Traffic for each IP address will be routed over a different ISP in FIG.1B, namely ISP 141 for IP address 131 and ISP 142 for IP address 132.Which particular IP address is returned to end user device 101 by anassociated DNS lookup node can vary and in this example is selected bycontent delivery network 110, such as by a management node withincontent delivery network 110.

In a second example, DNS lookup 178 in FIG. 1C is performed by end userdevice 101 which returns an IP address associated with the desirednetwork content cached by content node 121. The IP address can be eitherIP address 133 or IP address 134 for FIG. 1C to reach content node 121.Traffic for each IP address will be routed over a different ISP in FIG.1B, namely ISP 141 for IP address 133 and ISP 142 for IP address 134.Which particular IP address is returned to end user device 101 by anassociated DNS lookup node can vary and in this example is selected bycontent delivery network 110, such as by a management node withincontent delivery network 110.

To select an ISP, content delivery network 110 can identify networkcharacteristics for end user devices, ISPs 141-142, and content nodes,such as content nodes 120-121. For example, content delivery network 110can observe which of ISPs 141-142 is faster or has lower responselatency for content delivery for some set of end user devices. Contentdelivery network 110 processes the network characteristics and thedomain name lookup request to select an IP address with which end userdevice 101 reaches cached content on content nodes 120-121 or some othercontent node. Content delivery network 110 can inform a DNS lookupsystem of which IP address to return for specific domain names based onwhich ISP currently has the fastest or most desirable route to reach therequested content.

As shown in FIG. 1B, content node 120 supports IP addresses 131-132.Content delivery network 110 selects (210) among IP addresses 131-132for delivery of content to an end user device for content cached bycontent node 120. Although IP addresses 131-132 identify the samecontent node 120, a content request destined for IP address 131 istransferred through a different ISP than a content request destined forIP address 132. This is because IP addresses 131-132 differ in someparticular bits which are respectively are associated with differentshort prefixes A and B.

As shown in FIG. 1C, content node 121 supports IP addresses 133-134.Content delivery network 110 selects (210) among IP addresses 133-134for delivery of content to an end user device for content cached bycontent node 121. Although IP addresses 133-134 identify the samecontent node 121, a content request destined for IP address 133 istransferred through a different ISP than a content request destined forIP address 134. This is because IP addresses 133-134 differ in someparticular bits which are respectively are associated with differentshort prefixes A and B.

The network characteristics or network fastness as mentioned above canrefer to different factors. For example, content delivery network 110can identify predicted network performance for communications exchangedbetween any end user devices and any content nodes such as content nodes120-121. Predicted network performance may regard datagram transit time,throughput, response latency, connection establishment delay, price, ora combination of these. Predicted network performance may be based onpast or present measurements made by end user devices, content deliverynetwork 110, content nodes such as content nodes 120-121, or some otherdevice that can communicate with the content nodes through Internet 150.Measurements may be made using content requests, ICMP pings, traceroute,or other network interactions. Measurements may be raw or derived andconsider statistical concepts, such as peak, mean, median, and the like.

Network conditions affect IP address and prefix selection. For example,if ISP 141 begins to show signs of operational stress, includingfailures to exceed quality thresholds or response latency thresholds,content delivery network 110 could curtail or discontinue informing enduser devices that content node 120 is reachable at IP address 131.Content delivery network 110 informs (211) a DNS system that providesDNS lookup services for end user device 101 of a selected one of IPaddresses 131-134, where the selection is based in part on which ISP orcontent node currently has the more desirable network characteristics.Content delivery network 110 can thus shape traffic in real timeaccording to cost and quality constraints.

Continuing the discussion of FIG. 2B, once end user device 101 hasreceived IP address information to retrieve content, end user device 101transfers a content request for delivery to the IP address of theassociated content node over link 184. Internet 150, or routing elementstherein, receives (212) the content request transferred by end userdevice 101 for content cached by content delivery network 110. Therouting elements of Internet 150 identifies (213) route information forthe content request based on the previously received announcementmessages, such as announcement messages 171-172. In a first example, thepreviously received announcement messages indicate that trafficaddressed for IP addresses 131 and 133 are to be routed over ISP 141 andtraffic addressed for IP addresses 132 and 134 are to be routed over ISP142. Thus, Internet 150 transfers (214) content request for delivery tocontent node over selected ISP based on route information and the IPaddress of the content request.

To transfer or route the traffic associated with the content request,routing elements within Internet 150 determine that the destination IPaddress associated with the content request is associated with aparticular short prefix group, as previously indicated in announcementmessages or notifications. Elements within Internet 150 will route thepackets associated with the content request for delivery to ISP 141 ifthe destination IP address of the content request falls within the shortprefix group for ISP 141. Likewise, elements within Internet 150 willroute the packets associated with the content request for delivery toISP 142 if the destination IP address of the content request fallswithin the short prefix group of ISP 142.

A content node in content delivery network 110 receives (215) thecontent request and responsively provides content for delivery to enduser device 101. The particular content node that receives the contentrequest depends upon the destination IP address included in the contentrequest, such as the IP address provided by the DNS service responsiveto the DNS lookup of end user device 101. The content provided can beany network content as indicated in the content request, such as webpage content, multimedia content, pictures, and the like. Theappropriate content node transfers the content over any of ISP 141-142for delivery to end user device 101.

Using the prefix announcement processes described herein, the IPaddresses assigned to the content nodes can include IP addresses thatare in a tight address space grouping, as well as allow for routingcontrol over which ISP that content requests are routed. For example, IPaddress 131 and IP address 133 can be included within the same shortprefix IP address space, but be in different long prefix address spaces.Specifically, for a full IP address, then IP address 131 and IP address133 include the same first bits (corresponding to the short prefix) butcan differ in the remaining bits (corresponding to the long prefix).Thus, the short prefix can be used for both content node 120 and contentnode 121. The short prefix is propagated by content delivery network 110to an associated ISP, such as ISP 141, which responsively propagates theshort prefix to routing elements of Internet 150. When content requestsare issued by end user devices for an IP address falling within theshort prefix address space associated with ISP 141, then these contentrequests are routed to ISP 141 by Internet 150. Likewise, the differentshort prefix portions, which are not propagated by ISP 141 to Internet150, are propagated to ISP 141, and ISP 141 builds internal routingprocedures to route IP addresses that fall within these different shortprefixes to different content nodes. Advantageously, content deliverynetwork 110 can control routing of content requests for content nodesusing the prefix notation. Furthermore, content delivery network 110 canuse less IP address space by using the same short prefix for all contentrequests routed over a particular ISP, while still ensuring the contentrequests can be routed to different cache nodes using that sameparticular ISP by employing different short prefixes for differentcontent nodes.

Returning to the elements of FIG. 1, content delivery network (CDN) 110comprises one or more content nodes, network routing equipment, packethandling equipment, network links, management systems, and otherelements. Content delivery network 110 handles delivery of networkcontent to end user devices, such as end user device 101. The networkcontent includes web content, media content, videos, audio, pictures,news, database information, and the like. Content nodes of contentdelivery network 110, such as content nodes 120-121, cache content fordelivery to end user devices. The content can be originated at variousother systems, such as origin server 190. In some examples, networkcontent includes dynamic network content, and processes executed bycontent nodes 120-121 create the dynamic content.

Content nodes 120-121 can each include communication interfaces, networkinterfaces, processing systems, computer systems, microprocessors,storage systems, storage media, or some other processing devices orsoftware systems, and can be distributed among multiple devices.Examples of content nodes 120-121 can each include software such as anoperating system, logs, databases, utilities, drivers, caching software,networking software, and other software stored on non-transitorycomputer-readable media.

Internet Service Providers (ISP) 141-142 each comprise one or morepacket networks configured to route packet communications betweenendpoints over network links. ISPs 141-142 can include routers, bridges,switches, management systems, network links, and other network routingand handling equipment, including combinations thereof. Typically, eachISP is operated by a distinct service operator or company to provideInternet access services to a variety of customers. In some examples,each of ISPs 141-142 comprise long-haul communication service providersand route packet communications over network links between smaller localISPs.

Internet 150 comprises one or more packet networks and computernetworking systems configured to route packet communications betweenendpoints. In some examples, Internet 150 includes one or more ISPs overwhich communications are transferred, and can include a local ISP overwhich end user device 101 can access Internet 150.

End user device 101 comprises a computing device that can requestnetwork content. End user device 101 can include a computer, computingsystem, tablet, smartphone, web browser, game console, network client,terminal device, or other end user device. In many examples, end userdevice 101 includes user interface elements, such as a graphical userinterface or command line interface, through which a user can browse andrequest network content. End user device 101 can also include softwareapplications, operating systems, network interface cards, transceivers,processing circuitry, and non-transitory computer-readable media, amongother elements.

Origin server 190 can include communication interfaces, networkinterfaces, processing systems, computer systems, microprocessors,storage systems, storage media, or some other processing devices orsoftware systems, and can be distributed among multiple devices.Examples of origin server 190 can include software such as an operatingsystem, logs, databases, utilities, drivers, caching software,networking software, and other software stored on non-transitorycomputer-readable media.

Communication links 180-185 each use metal, glass, optical, air, space,or some other material as the transport media. Communication links180-185 can each use various communication protocols, such as TimeDivision Multiplex (TDM), asynchronous transfer mode (ATM), InternetProtocol (IP), Ethernet, synchronous optical networking (SONET), hybridfiber-coax (HFC), circuit-switched, communication signaling, wirelesscommunications, or some other communication format, includingcombinations, improvements, or variations thereof. Communication links180-185 can each be a direct link or can include intermediate networks,systems, or devices, and can include a logical network link transportedover multiple physical links. Although one main link for each of links180-185 is shown in FIGS. 1A-1C, it should be understood that links180-185 are merely illustrative to show communication modes or accesspathways. In other examples, further links can be shown, with portionsof the further links shared and used for different communicationsessions or different content types, among other configurations.Communication links 180-185 can each include many different signalssharing the same associated link, as represented by the associated linesin FIGS. 1A-1C, comprising resource blocks, access channels, pagingchannels, notification channels, forward links, reverse links, usercommunications, communication sessions, overhead communications, carrierfrequencies, other channels, timeslots, spreading codes, transportationports, logical transportation links, network sockets, packets, orcommunication directions.

As an example employing a content delivery network with 24-bit and27-bit CIDR prefixes, FIG. 3 is presented. FIG. 3 demonstrates datacenter selection based on a 27-bit CIDR prefix and ISP selection basedon a 24-bit CIDR prefix. FIG. 3 is a system diagram illustratingcommunication system 300. Communication system 300 includes Internetservice providers (ISP) 305-308, content delivery network 309, domainname service (DNS) 304, and at least one end user device 330. FIG. 3illustrates prefix announcements made by content delivery network 309and content requests made by end user device 330. Content deliverynetwork 309 includes one or more cache nodes such as nodes 310-311 andone or more management systems 302. Cache node 310 resides in datacenter A. Cache node 311 resides in data center B. Cache nodes 310-311can be examples of the content nodes discussed herein, such as contentnodes 120-121 in FIGS. 1A-1C, although variations are possible.Management system 302 can be included in the equipment of any of cachenodes 310-311.

Links 341-349 each comprise wired, optical, or wireless packet networklinks that carry IP traffic between the associated endpoints in FIG. 3.Links 341-349 can further include one or more communication links,routing systems, bridges, switches, modems, and the like, along withassociated control and management systems. In some examples, ones oflinks 341-349 comprise software or logical links.

Management system 302 can include communication interfaces, networkinterfaces, processing systems, computer systems, microprocessors,storage systems, storage media, or some other processing devices orsoftware systems, and can be distributed among multiple devices.Examples of management system 302 can include software such as anoperating system, logs, databases, utilities, drivers, caching software,networking software, and other software stored on non-transitorycomputer-readable media.

Internet Service Providers (ISP) 305-308 each comprise one or morepacket networks configured to route packet communications betweenendpoints over network links. ISPs 305-308 can include routers, bridges,switches, management systems, network links, and other network routingand handling equipment, including combinations thereof. Typically, eachISP is operated by a distinct service operator or company to provideInternet access services to a variety of customers. In this example,each of ISPs 306-308 comprise long-haul communication service providersand route packet communications over backbone network links betweensmaller local ISPs. ISP 305 comprises a local ISP over which end userdevice 330 receives service access to the Internet. In some examples,DNS system 304 is included in ISP 305. In other examples, a two-tier DNSlookup is employed, with DNS system 304 configured to communicate with aDNS system in content delivery network 309 to perform IP address lookupoperations.

End user device 330 comprises a computing device that can requestnetwork content. End user device 330 can include a computer, computingsystem, tablet, smartphone, web browser, game console, network client,terminal device, or other end user device. In many examples, end userdevice 330 includes user interface elements, such as a graphical userinterface or command line interface, through which a user can browse andrequest network content. End user device 330 can also include softwareapplications, operating systems, network interface cards, transceivers,processing circuitry, and non-transitory computer-readable media, amongother elements.

DNS system 304 performs IP address translation services for end userdevices, such as translating domain names into IP addresses. In someexamples, DNS system 304 delegates domain name translation to anotherDNS system, such as one included in content delivery network 309. Insuch examples, the delegated DNS system in content delivery network 309can be included in management system 302. DNS system 304 can includecommunication interfaces, network interfaces, processing systems,computer systems, microprocessors, storage systems, storage media, orsome other processing devices or software systems, and can bedistributed among multiple devices. Examples of DNS system 304 caninclude software such as an operating system, logs, databases,utilities, drivers, caching software, networking software, and othersoftware stored on non-transitory computer-readable media.

In operation, content delivery network 309 has a router or computingsystem, such as management system 302, that announces CIDR prefixes toInternet service providers 306-308 for use in routing content requeststo cache nodes 310-311. A prefix announcement may be a prefixannouncement message that indicates the prefixes along with associatedrouting information. A prefix announcement may be an IP routeadvertisement communicated to an Internet service provider along thecontrol plane of a routing protocol such as the Border Gateway Protocol,among other protocols and messaging types.

One example prefixes announcement process is as follows. Managementsystem 302 of content delivery network 309 transmits 24-bit and 27-bitCIDR prefix announcements to Internet service providers 306-308 overrespective network links 341-343, which are labeled accordingly in FIG.3. Table 380 of FIG. 4 indicates that content delivery network 309transmits to Internet service provider 307 24-bit prefix 313 and 27-bitprefixes 315-316. Although not shown, Internet service providers 306-308propagate to the Internet those announcements they receive that have a24-bit CIDR prefix. In this example, the 24-bit CIDR prefixes associatedwith each of ISPs 306-309 are announced to at least ISP 305. HoweverInternet service providers 306-308 do not propagate to the Internet orISP 305 those announcements they receive that have a 27-bit CIDR prefix.Such selective propagation to the Internet or ISP 305 of announcementsaffects how routing is performed for content requests traveling throughthe Internet or ISP 305 which are destined for cache nodes 310-311. TheInternet or ISP 305 uses the 24-bit CIDR prefixes to select one ofInternet service providers 307-308 when routing content requests tocache nodes 310-311. A content request having 24-bit CIDR prefix 312 isrouted through Internet service provider 306. A content request having24-bit CIDR prefix 313 is routed through Internet service provider 307.A content request having a 24-bit CIDR prefix 314 is routed throughInternet service provider 308. In this example, 27-bit prefixes areemployed for data center selection, and thus an Internet serviceprovider is configured with a 27-bit prefix is associated withassociated data centers. Associations between prefixes and data centersmay be encoded in the 27-bit prefix announcements or otherwiseconfigured within the associated Internet service provider.

Content request routing can occur as follows. End user device 330 seeksnetwork content cached in content delivery network 309, such as througha web browsing application executed on end user device 330. Before enduser device 330 issues a content request, DNS 304 informs end userdevice 330 of a selected IP address, such as through a domain namelookup process. The selected IP address is associated with a 24-bit CIDRprefix. In this example, DNS 304 selects IP address 322 which isassociated with 24-bit CIDR prefix 313, perhaps because Internet serviceprovider 307 and data center A have network conditions that exceed anetwork performance threshold. Other factors can be employed in IPaddress selection for a content request, as discussed herein. DNS 304can provide both an IP address and a prefix responsive to a domain namelookup issued by an end user device, although in some examples only anIP address is provided. End user device 330 transfers the contentrequest for delivery to the selected IP address, along with any prefixif provided by DNS 304. If data center A begins to show signs ofoperational stress, including failures to meet quality thresholds, DNS304 could curtail or discontinue informing end user devices to use IPaddresses hosted in data center A. DNS 304 can rebalance the load ofcontent requests between data centers by suggesting IP address 323hosted in data center B. Because IP addresses 322-323 are hosted indifferent data centers, IP addresses 322-323 do not share a 27-bitprefix.

ISP 305 initially receives the content request transferred by end userdevice 330 and identifies the destination IP address of the contentrequest as associated with a 24-bit prefix of a particular one of ISP306-308. ISP 305 then routes the content request through the particularone of ISP 306-308. When one or ISP 306-308 receive the content requesttransferred by end user device 330, the associated ISP 306-308 routes acontent request for delivery to a data center indicated by the IPaddress of the content request. Although Internet service providers306-308 receive from ISP 305 content requests destined for an IP addressthat falls within an associated 24-bit CIDR prefixes, these Internetservice providers instead use the corresponding 27-bit CIDR prefix toroute the content requests into content delivery network 309. ISPs306-308 may accomplish this according to CIDR notation which declares aprefix size. When the ISP receives a content request from ISP 305, thecontent request can include a destination IP address in CIDR notationdeclaring a prefix size of 24. By replacing the prefix size 24 with aprefix size 27 and without otherwise altering the destination IPaddress, the ISP routes the content request to content delivery network309 according to a 27-bit CIDR prefix. Because ISPs 306-308 have beenconfigured to determine which 27-bit prefix is associated with whichdata center, ISPs 306-308 are able to route content requests to datacenters using the 27-bit CIDR prefix.

Using the prefix announcement processes described herein, the IPaddresses assigned to each cache node can include IP addresses that arein a tight address space grouping, as well as allow for routing controlover which ISP and data center that content requests are routed. Forexample, IP address 322 and IP address 323 can be included within thesame 24-bit IP address space, but be in different 27-bit address spaces.Specifically, for a 32-bit IP address, then IP address 322 and IPaddress 323 include the same first 24 bits but can differ in theremaining 8 bits. Thus, /24 CIDR prefix 313 is used for both cache node310 of data center A and cache node 311 of data center B, even thoughdata center A and data center B might be geographically distant. The24-bit portion is propagated by content delivery network 309 to anassociated ISP, such as ISP 307, which responsively propagates the24-bit portion to the Internet at large, such as ISP 305, among otherrouting elements. When content requests are issued by end user devicesfor an IP address falling within the 24-bit address space of /24 CIDRprefix 313, then these content requests are routed to ISP 307 by theInternet or ISP 305. Likewise, the different 27-bit portions (/27 CIDRprefix 315 and /27 CIDR prefix 316), which are not propagated by ISP 307to the Internet at large, are propagated to ISP 307, and ISP 307 buildsinternal routing procedures to route IP addresses that fall within thesedifferent 27-bit portions to different data centers, namely data centerA and data center B. Advantageously, content delivery network 309 cancontrol routing of content requests for cache nodes in data center A anddata center B using the prefix notation. Furthermore, content deliverynetwork 309 can use less IP address space by using the same /24 CIDRprefix for all content requests routed over a particular ISP, whilestill ensuring the content requests can be routed to different datacenters using that same particular ISP by employing different /27 CIDRprefixes for different data centers. Although different data centers areemployed in FIG. 3, it should be understood that the same processes canapply to different cache nodes as well.

The example shown in FIG. 3 discusses 27 and 24 bit CIDR prefixes. Forother topologies CIDR prefixes with other prefix sizes are appropriate.Although this example shows announcements of CIDR prefixes of both sizesoriginating from content delivery network 309, an implementation ofcommunication system 300 may instead announce only the longer CIDRprefixes from content delivery network 310, and Internet serviceproviders 306-308 may automatically derive the shorter CIDR prefixesfrom the longer CIDR prefixes. In yet another implementation theInternet service providers may announce the longer CIDR prefixes as-isand not the shorter CIDR prefixes.

FIG. 5 is a sequence diagram illustrating a method of operatingcommunication system 300 of FIG. 3. Elements shown in FIG. 5 operate touse IP addresses and CIDR prefixes. Communication system 100 of FIG. 1Cmay also perform the behavior shown in FIG. 5. During this example, enduser device 330 attempts to retrieve content residing on cache node 311.

Initially DNS 304 instructs end user device 330 to use IP address 322which is associated with 24-bit CIDR prefix 313 to reach content oncache node 310. End user device 330 issues (501) a content requestdirected to that address over link 347 in FIG. 3. Because IP address 322is associated with a 24-bit CIDR prefix 313, ISP 305 routs the contentrequest to ISP 307 over pathway 371 in FIG. 3. ISP 307 forwards (502)the content request, but replaces the prefix size of 24 with a prefixsize of 27 to produce 27-bit CIDR prefix 315. ISP 307 is configured toroute IP addresses for that 27-bit prefix 315 for delivery to datacenter A, and accordingly routes the content request over pathway 372.Cache node 310 receives the content request and responds (503) with thedesired content, which is delivered (504) to end user device 330.Although this example shows the content request and content responsebeing routed through the same ISP 307, any other route may instead beused for delivering the content response.

Later, the fastest data center changes from data center A to data centerB. Responsive to domain name translation requests, DNS 304 now instructsend user device 330 to use IP address 323 associated with 24-bit CIDRprefix 313 to reach content on cache node 311. End user device 330issues (511) a content request directed to that address over link 347 inFIG. 3. Because IP address 323 is associated with a 24-bit CIDR prefix313, ISP 305 routes the content request to ISP 307 over pathway 371 inFIG. 3. ISP 307 forwards (512) the content request, but replaces theprefix size of 24 with a prefix size of 27 to produce 27-bit CIDR prefix316. ISP 307 forwards (512) the content request, but replaces the prefixsize of 24 with a prefix size of 27 to produce 27-bit CIDR prefix 316.ISP 307 is configured to determine that 27-bit prefix 316 is associatedwith data center B and accordingly routes the content request overpathway 373. Cache node 311 receives the content request and responds(513) with the desired content, which is delivered (514) to end userdevice 330.

As a further example of the operation of communication system 300, FIG.6 is presented. FIG. 6 is a sequence diagram illustrating a method ofoperating communication system 300 of FIG. 3. Elements shown in FIG. 6operate to use IP addresses and CIDR prefixes. Communication system 100of FIG. 1C may also perform the behavior shown in FIG. 6. During thisexample, end user device 330 attempts to retrieve content residing oncache node 311.

Initially DNS 304 instructs end user device 330 to use IP address 321which is associated with 24-bit CIDR prefix 312 to reach content oncache node 310. End user device 330 issues (601) a content requestdirected to that address over link 347 in FIG. 3. Because IP address 321is associated with a 24-bit CIDR prefix 312, ISP 305 routes the contentrequest to ISP 306 over pathway 374 in FIG. 3. ISP 306 forwards (602)the content request, but replaces the prefix size of 24 with a prefixsize of 27 to produce 27-bit CIDR prefix 318. ISP 306 is configured toroute IP addresses for that 27-bit prefix 318 for delivery to datacenter A, and accordingly routes the content request over pathway 375.Cache node 310 receives the content request and responds (603) with thedesired content, which is delivered (604) to end user device 330.Although this example shows the content request and content responsebeing routed through the same ISP 306, any other route may instead beused for delivering the content response.

Later, the fastest data center changes from data center A to data centerB. Responsive to domain name translation requests, DNS 304 now instructsend user device 330 to use IP address 324 associated with 24-bit CIDRprefix 314 to reach content on cache node 311. End user device 330issues (611) a content request directed to that address over link 347 inFIG. 3. Because IP address 324 is associated with a 24-bit CIDR prefix314, ISP 305 routes the content request to ISP 308 over pathway 376 inFIG. 3. ISP 308 forwards (612) the content request, but replaces theprefix size of 24 with a prefix size of 27 to produce 27-bit CIDR prefix317. ISP 308 is configured to determine that 27-bit prefix 317 isassociated with data center B and accordingly routes the content requestover pathway 377. Cache node 311 receives the content request andresponds (613) with the desired content, which is delivered (614) to enduser device 330.

FIG. 7 illustrates the internal configuration of management system 700.Management system 700 can be an implementation of elements of contentdelivery network 110, such as portions of content nodes 120-121 in FIGS.1A-1C, or management system 302 in FIG. 3, although variations arepossible. Management system 700 includes management interface 710,communication interface 720, and processing system 730. Processingsystem 730 includes processor 740 and storage system 750. In operation,processing system 730 is operatively linked to management interface 710,communication interface 720, and storage system 750. Processing system730 is capable of executing software 760 stored in storage system 750.When executing the software, processing system 730 drives managementsystem 700 to operate as described herein. Management system 700 canalso include other elements, such as user interfaces, computer systems,databases, distributed storage and processing elements, and the like.

Management interface 710 includes one or more network interfaces fortransferring announcement messages for delivery to ISPs and associatednetwork equipment.

Management interface 710 can comprise software interfaces, applicationprogramming interfaces (APIs), remote user interfaces, terminalinterfaces, and the like. In some examples, management interface 710 isimplemented by processing system 730 and communicates over networkinterface 720. In other examples, management interface 710 is configuredto communicate over communication networks, such as packet networks, theInternet, and the like. Management interface 710 can include one or morelocal or wide area network communication interfaces which cancommunicate over Ethernet or Internet protocol (IP) links. Managementinterface 710 can include network interfaces configured to communicateusing one or more network addresses, which can be associated withdifferent network links. Examples of management interface 710 includenetwork interface card equipment, transceivers, modems, and othercommunication circuitry.

Network interface 720 includes one or more network interfaces forcommunicating over communication networks, such as packet networks, theInternet, and the like. The network interfaces can include one or morelocal or wide area network communication interfaces which cancommunicate over Ethernet or Internet protocol (IP) links. Networkinterface 720 can include network interfaces configured to communicateusing one or more network addresses, which can be associated withdifferent network links. Examples of network interface 720 includenetwork interface card equipment, transceivers, modems, and othercommunication circuitry.

Processing system 730 can be implemented within a single processingdevice but can also be distributed across multiple processing devices orsub-systems that cooperate in executing program instructions. Examplesof processing system 730 include general purpose central processingunits, microprocessors, application specific processors, and logicdevices, as well as any other type of processing device. In someexamples, processing system 730 includes physically distributedprocessing devices, such as cloud computing systems.

Storage system 750 comprises one or more computer-readable media-baseddata storage system, although variations are possible. Storage system750 can comprise any non-transitory storage media readable by processor740 and capable of storing at least software 760. Storage system 750 caninclude volatile and nonvolatile, removable and non-removable mediaimplemented in any method or technology for storage of information, suchas computer readable instructions, data structures, program modules, orother data. Storage system 750 can include non-volatile storage media,such as solid state storage media, flash memory, or solid state storagesystem. Storage system 750 can be implemented as a single storage devicebut can also be implemented across multiple storage devices orsub-systems. Storage system 750 can comprise additional elements, suchas controllers, capable of communicating with processor 740.

Software stored on or in storage system 750 can comprise computerprogram instructions, firmware, or some other form of machine-readableprocessing instructions having processes that when executed byprocessing system 730 direct management system 700 to operate asdescribed herein. For example, software drives management system 700 toassign content nodes to be associated with one or more IP addresses witha short prefix and a long prefix, and announce network routing messagesthat indicate the long prefixes and short prefixes to packet networkrouting systems, such as elements of ISPs 120-121 in FIGS. 1A-1C or ISPs306-308 of FIG. 3, among other operations. The software can also includeuser software applications. The software can be implemented as a singleapplication or as multiple applications. In general, the software can,when loaded into processing system 730 and executed, transformprocessing system 730 from a general-purpose device into aspecial-purpose device customized as described herein.

In at least a first example, the machine-readable processinginstructions comprise CIDR announcement logic 770, which can includeuser interface module 771, CIDR prefix module 772, and routing controlplane module 773. Implementations of CIDR announcement logic 770 haveflexibility as to how many logic modules are present and howresponsibilities are distributed amongst the modules. User interfacemodule 771 is configured to interact with a user to configure variousparameters associated with management of content nodes, such asreceiving IP address assignments for content nodes and identifying whichISPs are linked to a content delivery network, among other operations.User interface module 771 can communicate with management interface 710for manual or automated entry and maintenance of IP addressing data,such as the IP addresses of cache nodes, CIDR prefix sizes, and theassociation of CIDR prefixes with Internet service providers. CIDRprefix module 772 can determine CIDR prefixes for one or more IPaddresses associated with one or more content nodes, and determine shortand long prefixes, such as 24-bit and 27-bit CIDR prefixes, for deliveryto routing systems within one or more ISPs. CIDR prefix module 772analyzes the IP addresses of cache nodes and CIDR prefix sizes toextract 24-bit and 27-bit CIDR prefixes or CIDR prefixes of other sizesas appropriate to a given network topology. Routing control plane module773 distributes CIDR announcement messages for delivery to ISPs and theInternet, among other destinations. Routing control plane module 773 candelivery routing and handling configuration messages to other routingdevices over network interface 720, such as the prefix announcementmessages discussed herein. Routing control plane module 773 announcesrouting data such as CIDR prefixes, perhaps as Border Gateway Protocoladvertisements.

In at least a second example, management system 700 provides routeselection features which can drive a DNS system to return a particularIP address or prefix responsive to content request domain name lookuprequests from end user devices. For example, when management system 700comprises features of one or more of DNS system 304 or management system302 of FIG. 3, route selection can be handled by management system 302.The machine-readable processing instructions comprise route selectionlogic 780, which can include conditions monitoring module 781 andaddress selection module 782. Conditions monitoring module 781 isconfigured to monitor conditions of various routes over which contentnodes can be reached. These various routes can include various ISPs. Theconditions can include network conditions such as response latency ofcontent request fulfilment, throughput of an ISP, bandwidth of linksassociated with an ISP, throttling status of an ISP, or the networkcharacteristics and network conditions discussed in FIGS. 1A-1C,including combinations and variations thereof. The conditions monitoringcan be performed by continual or periodic traffic monitoring for contentrequests handled by content nodes of an associated content deliverynetwork. Network performance information can be received from contentnodes which monitor their own performance and report network conditionsto management system 700. Network performance information can beidentified by management system 700 by issuing pings, dummy traffic,test traffic, or other monitoring traffic. Conditions monitoring module781 can identify a desired ISP over which to handle content requests,and can identify a desired data center that includes content nodes orcache nodes. These desired ISPs or desired data centers can beidentified based on the network conditions monitored or collected byconditions monitoring module 781. A desired IP address of a content nodeor prefix of a particular ISP can be identified and provided to a DNSlookup service. As an example DNS lookup service, address selectionmodule 782 is provided. Address selection module 782 can receive aselected or desired IP address or prefix from conditions monitoringmodule 781. Responsive to domain name translation requests issued by enduser devices related to content requests, address selection module 782can provide the desired or selected IP address or prefix to an end userdevice. In some examples, a main DNS service is employed by an ISP toinitially identify management system 700 as a sub-DNS or secondary DNSlookup service. The secondary DNS lookup service can respond to addresstranslation requests issued by another primary DNS service with thedesired or selected IP address that identifies a desired data center ordesired content node. In some examples, the secondary DNS lookup servicecan respond to address translation requests issued by another primaryDNS service with the desired or selected IP address as well as a prefix,such as a 24-bit prefix, which identifies an ISP over which theassociated content request is to be routed.

The included descriptions and figures depict specific embodiments toteach those skilled in the art how to make and use the best mode. Forthe purpose of teaching inventive principles, some conventional aspectshave been simplified or omitted. Those skilled in the art willappreciate variations from these embodiments that fall within the scopeof the invention. Those skilled in the art will also appreciate that thefeatures described above can be combined in various ways to formmultiple embodiments. As a result, the invention is not limited to thespecific embodiments described above, but only by the claims and theirequivalents.

What is claimed is:
 1. A method of operating a content delivery networkcomprising: assigning, to a content node of the content deliverynetwork, a network address having a short prefix and a long prefix;assigning, to an additional content node of the content deliverynetwork, a different network address having the short prefix and adifferent long prefix; announcing the network address to an Internetservice provider without announcing the long prefix, such that theInternet service provider announces only the short prefix to otherInternet service providers; announcing the network address to theInternet service provider, including announcing the short prefix and thelong prefix; and announcing the different network address to theInternet service provider, including announcing the short prefix and thedifferent long prefix.
 2. The method of claim 1 wherein announcing thenetwork address and the different network address to the Internetservice provider occurs subsequent to announcing the network address tothe Internet service provider without announcing the long prefix.
 3. Themethod of claim 2, wherein the short prefix comprises a 24-bit classlessinter-domain routing (CIDR) prefix, and wherein the long prefixcomprises a 27-bit CIDR prefix.
 4. The method of claim 3, wherein thedifferent prefix comprises different 27-bit CIDR prefix.
 5. The methodof claim 1 further comprising: assigning, to the content node of thecontent delivery network, a second network address having a second shortprefix and a second long prefix; and announcing the second networkaddress to a second Internet service provider without announcing thesecond long prefix, such that the second Internet service providerannounces only the second short prefix to the other Internet serviceproviders.
 6. The method of claim 5 further comprising announcing thesecond network address to the second Internet service provider,including announcing the second short prefix and the second long prefix.7. The method of claim 6 further comprising: assigning, to theadditional node of the content delivery network, a third network addresshaving a third short prefix and a third long prefix; and announcing thethird network address to a third Internet service provider withoutannouncing the third long prefix, such that the third Internet serviceprovider announces only the third short prefix to the other Internetservice providers.
 8. The method of claim 7 further comprisingannouncing the third network address to the third Internet serviceprovider, including announcing the third short prefix and the third longprefix.
 9. The method of claim 8, wherein the Internet service providerannounces only the short prefix to Internet routing elements.
 10. Themethod of claim 9 wherein the second Internet service provider announcesonly the second short prefix to the Internet routing elements.
 11. Themethod of claim 10 wherein the short prefix instructs the Internetrouting elements to route content requests addressed to the networkaddress to the Internet service provider.
 12. The method of claim 11wherein the long prefix instructs the Internet service provider to routethe content requests to the content node.
 13. The method of claim 12wherein the different long prefix instructs the Internet serviceprovider to route the content requests to the additional content node.14. The method of claim 13 wherein the second short prefix instructs theInternet routing elements to route content requests addressed to thesecond network address to the second Internet service provider.
 15. Themethod of claim 14 wherein the second long prefix instructs the secondInternet service provider to route the content requests to theadditional content node.
 16. The method of claim 15 wherein the thirdshort prefix instructs the Internet routing elements to route contentrequests addressed to the third network address to the third Internetservice provider.
 17. The method of claim 16 wherein the third longprefix instructs the third Internet service provider to route thecontent requests to the additional content node.
 18. The method of claim17 further comprising: monitoring network conditions of at least theInternet service provider and the second Internet service provider;identifying a selected IP address from among the network address and thedifferent network address for end user devices to reach the contentnode; and instructing a domain name service (DNS) system to return theselected IP address responsive to domain name lookup requests forcontent cached by the content delivery network.
 19. The method of claim18, wherein the network conditions comprise a latency of contentrequests from the end user devices.
 20. The method of claim 19 whereinthe network address, the different network address, the second networkaddress, and third network address each comprises an Internet protocol(IP) address that differs relative to each other.